Which Do You Use?

Both! If you don't have a preference, then you can easily use both in certain situations. If you're not close to town but have some nice items in your bag, stop in at the nearest outpost, toss up your store, and go for a bio break. Save your biggest and best items, such as green or blue armor and weapons, for the broker as these tend to fetch quite a bit on the market but feel free to unload your smaller items wherever you happen to be and you will be rewarded with lighter bags and a heavier purse.